The chemistry is a central science, because it provides support to other sciences such as physics, biology, geology, petrochemical, etc. . Also lets meet human needs in different areas or fields of human activity. We have:

1) In medicine : Chemistry helps with the synthesis of different drugs (antibiotics , analgesics , antidepressants, vaccines, vitamins , hormones , radioisotopes, etc. ) , for the treatment of many diseases and to improving general health .

2) Nutrition: The chemical synthesis allows calls flavoring and coloring to improve certain properties of food substances , and thus can easily be ingested ; preservatives for food not deteriorate in a short time ; also determines the critical chemical substances requires the body ( minerals, vitamins , proteins, etc. )

3) Agriculture: With chemicals like fertilizers and fertilizer soil productivity is increased, and is able to meet the needs of increasingly growing food. In addition to the use of insecticides, fungicides and pesticides, many diseases and pests that affect crop possession.

4) In the textile and clothing care . Chemical potentially help meet this need , Synthesizing many textile fibers ( rayon, Orlon , nylon) , dyes for dyeing, washing substances (soaps , detergents, etc) preservatives of natural and synthetic fibers , etc. .

5) Environment: Helps in the treatment and control of pollutants that affect our ecosystem (water, soil and air) , and the assistance of environmental disasters such as oil spills, acid rain fall , forest fires, etc. .

6) archeology : Determining age of fossils .

7) In mineralogy : Techniques for extraction and purification of metals .

8) Astronomy : chemical fuels for rockets , clothes and food concentrates for astronauts .

9) industry and metallurgy : metallurgy in chemistry is important because it will serve for the manufacture of alloys and / or resistant to the development of various material objects : cars, columns for housing construction , spacecraft, ships , etc .

10) agribusiness : chemistry is important in agribusiness by allowing retrieval of cement, iron, oil , glass, plastic , etc. . . and this is used by man.

Positive and negative aspects of chemistry :

Negatives:

We used products on the market that , years later , have shown a negative environmental impact. For example , chlorofluorocarbons used in air conditioners , refrigerators , etc. . , Have been synthesized compounds lot of bad things, to do drugs ( Ecstasy) , explosives ( trinitrotoluene ) , poisonous compounds , etc. .. The big concern the possibility that terrorist organizations around the world use chemical weapons.

Positives

Insulation as polyurethane up to 80% reduced energy consumption in a home. The widespread installation of insulation in Europe would avoid the emission of 370 million tons of CO2.La chemistry applied to drugs has allowed extending the average life expectancy to 80.9 years. Madrid , for example , chemical compounds 82.Los detergents reduced to 2 hours 16 basic tasks hogar.En cleaning industry , the combination of chemicals is obtained , for example , greater lightness of the planes ( up to 30% ) and therefore a great saving of fuel . In cars, 100 kg of plastics and synthetic rubbers replace 360 kg of metal varios.La substance application in gene therapy combined with stem cells will see, diagnose and treat cancer that starts in the decade now

We performed a retrospective journey through time to discover the origins and evolution of chemical science .

Chemistry of old ( until the fourth century AD)

It is considered that it was in Egypt that had its origins chemistry; the ancient Egyptians mastered metallurgy , ceramics , glass manufacturing , dry cleaning, manufacture of perfumes and cosmetics.

In Egypt it was considered a chemical "divine science " , reserving his practice to the priests, who hid it jealously , nevertheless many chemical knowledge to other countries filtered , reaching Europe through Byzantium and then to Spain after being conquered by the Arabs ( 711 ) , this is where the word " chemistry" is transformed into "alchemy" by adding the prefix "al" characteristic of the Arabic language .

The Greek philosophers tried to give an explanation of the bodies, so based on the thesis of Plato and Empedocles , Aristotle of Stagira (year 384-332 BC) holds that the universe is made up of four elements : air, water, earth and fire .

Doctors at the time employed a limited knowledge of chemistry; known that alum, soda ,iron oxide, sulfur and blue vitriol were employed for therapeutic purposes. In the field of organic chemistry obtaining wheat starch was known, the extraction of turpentine , are able to obtain oil from seeds and fruits of olive , almond and castor .

Period of Alchemy (IV century to the sixteenth century AD)

Alchemists were set as main objective to achieve " Philosopher's Stone " understood as a substance in contact with the transform ordinary metals into gold. Also sought the "elixir of life" believed was a substance that when taken , preserved man from death , preserving eternal youth.

The brightest Arabic alchemist Geber was who lived and died in Seville in the late eighth century, considered one of the greatest sages of the world. Post-Geber are Rhases (X century), Avicenna (eleventh century) and Averroes (1126-1198).

Among the highlights Western alchemists first chronologically and by his wisdom San Alberto Magno ( 1193 or 1206-1280 ) , German Dominican Aristotle considered middle age . ; among later alchemists to mention :

§ Roger Bacon (1214 - 1294)

§ St. Thomas Aquinas (1225 - 1274) who wrote a treatise on the essence of the minerals and the other on the philosopher's stone .

§ Raymond Lully (1235 - 1315)

§ Basil Valentine (XV century) , etc. .

It was thought that metals were a combination of mercury and sulfur , plus the difference between them would be in the different proportions of these elements, but other noble metals such as silver and mercury would stand little sulfur.

According to this theory, there should be an agent, a kind of yeast that achieved in a common metal , removal of excess component with its subsequent transformation into gold.

Obviously no alchemists achieved their desired goal, but in the attempt largely developed chemical knowledge and achieved various alloys , knew the action of acids : sulfuric , hydrochloric and nitric , aqua regia which is a very strong solvent used was by alchemists .

Organic chemistry experience unites little momentum , the discovery of alcohol corresponds to this time .

The medicine was under the influence of Galen , one of the most remarkable ancient physicians , who gave written numerous special formulas for the preparation of many medicines out drugs from plants and animals.

They are the last alchemists those obtained in large quantity chemical preparations intended for healing purposes, initiating the period of Iatrochemistry .

Period of Iatrochemistry (XVI and XVII centuries)

The chemistry in this time becomes an auxiliary discipline of medicine, the most decisive influence exercised by the physician Paracelsus .

The iatroquimistas argue that man is composed of three elements: sulfur, mercury and salt; the "vital process " is considered a chemical process, such that the body in a healthy active body act on each other in precise proportions ; diseases are caused by abnormal predominance of any of the elements: and the plague and fever indicate a preponderance of mercury and irregular diarrhea and dropsy by dominance of salt.

Therapeutic mission was to treat the patient with chemical agents to achieve the restoration of the proportions necessary for the process of life.

The apothecaries become dynamic centers of experimentation , where the intangible search for new useful chemical preparations for use as drugs is manifested , but not always the iatroquimistas had good results with their patients.

Period of phlogiston theory (1700 - 1774)

Chemistry provides the basis for independent science ceased to be mere medical assistant , setting as the discipline that deals with the composition , transformation and unfolding of bodies, the study of phenomena that occur in these processes, the laws that governing and determining the properties of bodies by virtue of its composition.

Research from this period were primarily aimed at explaining the phenomenon of combustion , concluding the " phlogiston theory " , the most prominent of this theory is Stahl , who explains the transformation of all combustible bodies by fire as the same phenomenon because they all have a common constituent part of which is called " phlogiston " . A substance rich in phlogiston be more if it burns more easily and with greater flame, and the extraordinarily rich in phlogiston serious coal .

The fact that combust phosphorus and sulfur form an acid, why the idea that they were a combination of the corresponding acid with phlogiston , this idea metals by heat oxides are also extended .

Although the time of phlogiston is relatively short , there are chemicals featured in this period as : Boyle, Becher, Stahl, Cavendish, Priestley and Scheele . It is also necessary to highlight the great Russian chemist Mikhail Lomonosov (1711 - 1765) , whom many authors attribute was ahead of the discoveries of Lavoisier.

Time of Lavoisier (1774 - 1828)

The French chemist Antoine Laurent Lavoisier demonstrates his outstanding work done from 1775 to 1780, the combustion phenomenon is not due to the expulsion of " phlogiston " that is a decomposition , but rather a combination with air.

Lavoisier, in 1797 sets out the theory of combustion by three fundamental principles :

1. The bodies burn only in pure air

Two . This is consumed by combustion , the body weight gain burning equals weight loss of air.

Three . The fuel body is generally transformed , by virtue of their combination with fresh air , in an acid , but in the case of metals, metallic leading limes

Because of Lavoisier 's ideas, a revolution occurs in chemical concepts. Is using the balance feeding weight calculations in chemical processes , showing that an oxide weighs more than the pure metal; this is that if it had expelled its phlogiston should weigh less.

Period of development of organic chemistry (1828 - 1886)

The division of inorganic chemistry and organic or mineral is recognized , holding that organic substances have a "vital force" and that can only be produced in living organisms ; prominent advocate of this thesis was the Swede Johann Jakob Berzelius . In 1828 , the German Friedrich Wöhler produced urea ( organic compound ) by heating ammonium cyanate (inorganic compound ) , thus putting an end to the vitalistic theory.

It is found that all organic compounds have carbon . Highlights at this time : Robert Bunsen, Dumas Frankland , August Kekule , Hermann Kolbe , Liebig and Wurtz .

Theories developed to explain the properties of the compounds , as well as the experimental material widely progresses .

We study and synthesize the simplest hydrocarbons are organic compounds, also many other compounds of organic nature : alcohols , ethers , acids , ketones , amines, etc. .. Liebig and his colleagues performed a brilliant job in the chemistry of dyes , giving theoretical support to experimental work .

Finally the gas lighting and the paper ( 1846 ) was made , the latter from wood and straw.

Modern Chemistry

The beginning of the current chemical can place it in 1887 , coinciding with the publication by the Swedish Svante Arrhenius 's theory of electrolytic dissociation , ie the decomposition of a substance by the action of the electric current.

The chemistry is based on physics and mathematics to explain the chemical processes.

There are numerous characters who contributed greatly in chemistry during recent times , we will mention the most important :

1. Adolf von Baeyer (1835 -1917) , a disciple of Kekule and Bunsen contributed to organic chemistry , discovered and synthesized indigo quinoline investigated the structure of benzene and studied dyes.

2. Marcellin Berthelot (1827 - 1907) , investigated alcohols and carbohydrates synthesized acetylene , contributed in thermochemical and explosives .

3. Emil Fisher (1852 -1919) , discovered the uric acid and purine derivatives .

4. Dimitri Mendeleev (1834 - 1907) and Lothar Meyer (1830 - 1895) , established a periodic table based on atomic weights.

5. Wilhelm Ostwald (1853 -1932) , contributed to the study of the rates of reactions and the use of catalysts .

6. Henry Moseley (1887 -1915) , laid the foundations for the modern periodic table based on atomic numbers .

7. Alfred Nobel (1833 -1896) , Swedish chemist, inventor of dynamite.

8. Marie Curie (1867 -1934) , Polish-born chemical , radioactive substances study discovering the elements polonium and radium in 1898. He won the Nobel Prize in Chemistry in 1911.

9. Niels Bohr (1885 -1962) , laid the foundations for the modern concept of the atom , Nobel Prize in Physics in 1922.

10. Linus Pauling (born in 1901 ) , masterfully explained the chemical bond , introducing the term electronegativity, won the Nobel Prize in Chemistry in 1954 in recognition of his brave struggle against the military use of atomic energy , he was awarded the Nobel Prize peace in 1962.

We could go on listing the long list of all those who contributed their research to modern chemistry, but for reasons I will avoid extension .

The development achieved by the chemical in our time is clear , we are surrounded by chemicals, many of them man- synthesized included the wide distribution of synthetic polymers : plastics , polyethylene, Teflon , PVC, dacron , nylon , synthetic rubber etc.